Web MIDI: introduce WebMIDIClient API to request a permission

Source/core/platform/midi/MIDIAccessor.h

Index: Source/core/platform/midi/MIDIAccessor.h
diff --git a/Source/core/platform/midi/MIDIAccessor.h b/Source/core/platform/midi/MIDIAccessor.h
index 3eaa90c9362c42f9c96afcdd857b3607f6732c32..59f437a1ce7f9df2f87bda40c8f40acdeaa44af6 100644
--- a/Source/core/platform/midi/MIDIAccessor.h
+++ b/Source/core/platform/midi/MIDIAccessor.h
@@ -39,6 +39,7 @@
 namespace WebCore {
 
 class MIDIAccessorClient;
+class SecurityOrigin;
 
 class MIDIAccessor : public WebKit::WebMIDIAccessorClient {
 public:
@@ -50,6 +51,8 @@ public:
     void sendMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp);
 
     // WebKit::WebMIDIAccessorClient
+    virtual WebKit::WebSecurityOrigin securityOrigin() const OVERRIDE;
+
     virtual void didAddInputPort(const WebKit::WebString& id, const WebKit::WebString& manufacturer, const WebKit::WebString& name, const WebKit::WebString& version) OVERRIDE;
     virtual void didAddOutputPort(const WebKit::WebString& id, const WebKit::WebString& manufacturer, const WebKit::WebString& name, const WebKit::WebString& version) OVERRIDE;
     virtual void didAllowAccess() OVERRIDE;